1. Field of the Description
The present invention relates, in general, to projecting or displaying the illusion of video/animated or still three dimensional (3D) images, and, more particularly, to autostereoscopic projection systems such as those adapted to display ghost or latent 3D images as provided as part of a Pepper's ghost illusion.
2. Relevant Background
There are numerous entertainment and other settings where it is desirable to create a unique visual display. For example, theme or amusement parks may include rides or walk-through attractions where guests (or “viewers”) are entertained by a unique visual effect or illusion. Often, engineering challenges arise in fabricating and installing the display or projection system.
Pepper's ghost is an illusionary technique used by magicians, theatrical designers, ride or attraction designers, and others to produce a 3D illusion of a latent or ghost-like image. Using a reflective and transmissive element (e.g., a simple piece of reflective plate glass or a transparent polyester thin film) and special lighting techniques, Pepper's ghost systems can make objects appear and disappear within a scene or room. Generally, these systems include a main room or scene that is readily viewed by a guest or viewer and also include a hidden room that is not visible to the viewer. Both rooms may be identical in their physical structure including furniture and other objects except that the hidden room may include additional objects or characters such as a ghost. A large piece of glass, a half-silvered mirror, or other reflective element (e.g., a flexible sheet of polyester such as a polyethylene terephthalate (PET), a Mylar®, or the like) is situated between the viewer and the scene at an angle of 45 degrees. When the main room is lit and the hidden room is darkened, the viewer only sees the main room as the hidden room does not reflect from the glass, which is itself hard to see as it typically extends across the entire view of the main room and is transparent (at least in part) to allow viewing of the room behind the glass (or reflective element).
Pepper's ghost becomes visible to the viewer when the entire hidden room or portions, such as a “ghost” or other character, are brightly lit. Since only a portion of the light cast upon the ghost or other objects in the hidden room is reflected from the glass, the reflected images appear as latent or ghostly images relative to the objects in the main room (e.g., the reflected images or images superimposed in the visible room may appear to float). The Pepper's ghost image appears to be a 3D image that may be still or animation may be provided such as with animatronics or by placing a live actor in the hidden room. In some other implementations, the hidden room may be replaced by a projection assembly that projects a still or animated image onto a screen, such as a rear projection screen. Images on this projection screen (which is hidden from view from the viewer) are reflected from the glass or reflective element (or reflective surface of the reflective element which may be a half-silvered mirror or a flexible material (e.g., a polyester film such as a sheet of Mylar®) with similar optical qualities to provide a reflective surface).
When a flexible film or sheet of material (e.g., polyester) is used, the film needs to be tensioned (and held under tension during use) so that the reflective surface is optically flat. Some existing tensioning devices or assemblies require complex and cumbersome attachment hardware, and existing Pepper's ghost systems may require a large truss section to support just the tensioning device/assembly. Many tensioning assemblies rely upon compression sandwich-style plates to squeeze the film positioned between the films so that the film will be retained in the tensioning assembly without slipping out and while attempting to apply adequate tension forces to the film, both functions can be difficult to achieve and maintain in such assemblies. Other tensioning assemblies may require holes to be cut in the film for fasteners, which can limit any later desired lateral adjustments in tension and which can lead to tearing or cutting of the film as tension is applied or the film retained in place under tension. Still other assemblies may use abrasive surfaces on mating surfaces to grab onto the film and resist its movements, but, again, this can cause damage to the film and/or does not support localized adjustment of the tension along the length of the plates (e.g., have to mate the edge of the film with the abrasive surfaces of sandwich-style plates and then move the plates as a whole to adjust tension). While the industry has used these designs in the past and in current Pepper's ghost systems, there is continued dissatisfaction with features of each of these tensioning assemblies and/or techniques for flexible reflective elements (e.g., Mylar® sheets or the like).
Hence, there remains a need for improved designs for systems or assemblies for providing the Pepper's ghost illusion that provide high quality imagery over long time periods that are easy to maintain and install. Preferably such systems would be designed to simplify the attachment and tensioning process for a reflective element formed of a flexible polyester film/sheet, and the systems also preferably are useful for applying consistent tension on the film or reflective element.